The Promise
by A1t0Aria
Summary: People tend to say that Speed o' Sound Sonic's name is redundantly long, stupid even. But what if there's an origin behind that name of his that is far beyond our imagination? (Rated T because I'm paranoid.)


_Disclaimer: I do not own OPM._

 _Note: This is not a Sonic x OC fan fiction, because this is more of platonic love as compared to romantic love. However, if I do write a sequel to this, it may become a Sonic x OC fan fiction in the end._

 _Certain terms and part of the plot are a little confusing, but it is mostly because it will all only be explained if I ever write the sequel to this story._

 _Words in the story that are italicised are Sonic's thoughts, because this is a story based on his POV, but written in a third-person's POV._

 _With that, enjoy the story._

* * *

It began about twelve years ago, where Sonic was thirteen and still stayed at the ninja village. He had just finished his training for the day when he suddenly noticed someone coming up from behind him. On instincts, he swung one of his throwing knives at the unknown person who easily dodged the amateur's attempt.

 _Wait a minute... Even if I'm only a trainee, no average person should be able to dodge that! What's going on?_

"Ah! Can you be careful?" the person with a petite figure stepped out of the shadows with a confused look. "I'm not trying to hurt you! I promise!"

The boy with a topknot and purple streaks under his eyes focused his sharp gaze on the newcomer. It was a small girl with high, sea-blue twin tails that became white at the end and reached her shoulders. Her eyes were strangely of two different colours: a bright blue right eye and a golden left eye. A long purple scarf was wounded around her neck. She looked as if she was just about the age of a kindergartener, and had a bright smile on her face.

Sonic looked at her for a moment before he stepped away. "Get lost. I have no patience for pipsqueaks."

Panicking, the girl yelled from behind him, "Um... Can I train with you?"

He raised an eyebrow at her. He did not want to bother entertaining this kid, but maybe he should just play along to keep her from pestering him. "'Train'? I have just finished my training, Chibi. Plus, can you keep up with me?"

The girl smiled and flushed a little. "Well... I'm still not so good at combat too, but they said that I should be able to 'stretch my potential'... or something like that. I wonder what that means."

" _'They'_? Who the heck is _'they'_? Where did you come from, anyway? You don't look like someone from my village," Sonic pointed out.

"I came with a group of people who travel around the world together to train to become assassins!" she beamed innocently.

"... Brat, do you even know what the hell you're saying?"

"But that's what they told me!"

Sonic didn't know what to say. He had just met a random girl young enough to go to kindergarten who had just said that she was an assassin! What kind of reaction was normal for this kind of situation?!

"Fine," Sonic, who was still slightly dumbstruck, walked towards the girl and stared down at her. "I'll let you train here if you wanna, but don't expect me to train _with_ you."

The girl looked a little disappointed, but then she smiled brightly and reached her hand out towards Sonic.

"My name is Sonatina! I'm eight years old this year! How about you, Onii-san?"

 _Eight years old, huh? That's interesting. It seems like she's older than she looks. But I don't have anymore time to entertain her._

Sonic turned to walk back, replying, "I'm Sonic, thirteen years old. And don't call me 'Onii-san'."

Sonatina just stared at his back with her big curious eyes as Sonic walked away.

* * *

Sonic was exasperated.

Ever since that day, that strange-eyed girl with the purple scarf had came over to his training spot without fail. She tried her best not to interfere, but the fact that there was someone there just irritated him for some reason...

However, he had to admit that her agility was good for an eight-years-old kid. There were a few question on Sonic's mind regarding that girl, but he pushed them to the back of his mind.

Now exhausted from the training, the young ninja sat atop one of the tree branches and, dazed, silently watched Sonatina practice her skills. She was practicing with a rubber knife with ink and using a tree as her target, her purple scarf fluttering behind her like some sort of flag.

 _What kind of assassin would train using a rubber knife and a tree?!_ Sonic sighed and shook his head.

It was then when he saw something terrifying.

As Sonatina edged closer to the tree, she suddenly seemed to vanish into thin air before a shadow appeared in her place. The shadow loomed towards the tree before it suddenly zoomed past and slashed the tree. Sonic stared at the part of the tree that she had slashed marked out accurately with ink, wide-eyed.

 _What kind of move was that? Not even the strongest ninja in my village can literally transform into just a shadow like that without a smokescreen! Just... what is with this kid?_

It was at that moment when Sonic suddenly felt something slash at his throat from behind. He gasped and tried to move, but realised he had been immobilised. Red ink was dripping down from his neck when the knife came into contact with it. For some reason, Sonic felt as if he was truly killed.

Sonatina smiled eerily as she whispered, "Gotcha."

Sonic felt her press a pressure point on his neck before he realised that he could move again. He quickly jumped down from the branch and stared up at the grinning lass. How did he, a ninja, not notice her presence?

"What the hell was that?!" he asked her.

"Um... A skill I just learnt on my own to surprise my targets, I guess? I call it 'Killing Intent Manipulating'," she smiled at him, "I learnt that if you were to make your intent impossible to feel, you can actually blend into your surroundings like this."

Sonic was wide-eyed when he realised that she was vanishing like the Cheshire Cat from Alice in Wonderland right in front of his very eyes. No wonder he couldn't detect her.

"However, if my killing intent is very high, this is what happens that may confuse my target..."

Suddenly, Sonatina's figure appeared, but like a shadow with no features, which made a chill go down his spine. It was actually kind of creepy to know that she was someone who could kill him at any second whenever she was around.

Questions filled his mind. _What is the killing intent that Sonatina's talking about? Has it got to do with the 'they' she talked about that day?_

That was when the shadow dissipated to reveal Sonatina herself who jumped down from the branch that she was sitting on earlier. She stretched and muttered, "Uhh... I'm so tired... Today was a fun day, though! Thanks, Sonic Onii-san!"

Sonic had a look of disgust and shock on his face. What the hell was with that honorific which went along with his name? It sounded so awkward and embarrassing!

"I told you not to call me 'Onii-san'!" Sonic yelled in frustration.

"Then what do you want me to call you?" the young Sonatina asked him with a curious expression on her face.

"Just call me Sonic! That's enough!"

"Ok, Sonic... Onee-chan!" Sonatina started to double over in laughter.

"OI! I'M NOT A GIRL!"

* * *

It has been about a few weeks ever since Sonatina stepped into his training ground, and Sonic was quite impressed with her skills and agility. He suddenly had the urge to train with her, but didn't know how to request. After all, she's just a freaking eight-years-old, while he's thirteen!

 _Will she start to have the mindset that she's stronger than me?_

 _No! That can't happen! I'm training to become the strongest ninja in the world! She can't be stronger than me!_

 _... Right?_

"Um... Sonic Onii-san, why do you keep looking at me?"

He snapped out of his daze and realised that Sonatina had caught him red-handed. Well, so she's still using that honorific, huh...

His eyes narrowed as he walked over to her and said, "Brat, fight me."

"What?" Sonatina's huge eyes widened to what Sonic would have considered an impossible feat. How the heck did she do that? Her eyes were already so huge...

"But I'm still not strong yet... are you sure?" Sonatina asked worriedly.

Sonic nodded and took out his shurikens. "I'm anticipating to see just how strong you are, Chibi, 'cos my goal is to become the strongest person in the world."

"Um, can you please call me by my name instead?" Sonatina requested with a raised eyebrow.

But Sonic didn't listen to her request, and went for the kill. He tossed darts at her, which made her gasp and dodge quickly.

It was like a dance battle between the two, with them quickly prancing on their feet, trying to catch the other off-guard. However, Sonic soon gained the upper hand and successfully 'killed' Sonatina.

Looks like her skills were really still amateur.

Sonic was grinning. He was still the strongest, after all!

Sonatina sighed as she flopped against a tree while readjusting her scarf. "I knew my skills were still bad..."

Feeling relieved and now in a good mood, he sat down and leaned at the other side of the tree. The two of them were silent for a while as they rested after that sudden showdown of assassination skills.

"So... Why does your hair and eye colour look so weird?" Sonic asked her, feeling that now was the right time to ask the question burning at the back of his mind.

Sonatina replied after thinking for a few moments, "I guess it's a genetic defect..."

"... I see."

"So, why are you so bent on becoming the strongest?" Sonatina asked him.

"That's easy! It's because..."

The question suddenly hit Sonic like a ton of bricks. Now that he thought about it, why did he have that goal in mind in the first place? Why did he want to become strong?

"If you don't have a reason for what you want to do... What will you do once you've finally achieved that goal?" Sonatina asked again.

Sonic couldn't reply, because he didn't even know how he was supposed to answer that question of hers.

"By the way, Sonic Onii-san? Please don't smile like that next time. It's creepy."

* * *

Night fall. The forest was eerily dark, with the sound of strange insects filling the air once in a while. Sonic hid in one of the trees, waiting to strike his target - a raccoon.

After all, a ninja had to perfect his skills in any type of environment, regardless of the amount of light or whatnot.

As quietly as possible, he used his strong legs, leapt from his spot and shot a dart at the target, causing it to squeal in pain. With a dagger, he quickly dealt the final blow and silenced it, with a grin on his face. Blood splattered onto the floor.

Yep, that boy was one sadistic amateur ninja.

Tossing the body of the raccoon aside, Sonic continued on his way until he heard something that made him stop dead in his tracks.

A huge, shrilly scream pierced the peaceful night silence. Instinctively, Sonic quickly hid himself and slowly edged over to where the continuous screaming came from.

 _Who the hell would be screaming like this in the middle of the night?!_

It was only when he came to a clearing when he saw a nine-years-old Sonatina shrieking into the night sky, as if trying to rid of some frustration holding her down.

That's right, it has already been a year ever since he had first met that brat. Her presence was always annoying, but today, something seemed a little weird about it, especially since it was night time. Who the hell would decide to run to the forest and start screaming like some mad woman?

"Ho... HOLY SHIT!" Sonic almost screamed when he realised that he was at the edge of a lake and was about to fall in. He never knew how to swim, and he was going to be in big trouble if he really fell in.

It was then when the screaming ended and Sonatina fell to the ground, weeping.

The fourteen-years-old was taken aback by the scene in front of him. For the whole year, she had never cried no matter how bad her injuries were. Heck, he had even accidentally rammed a whole dagger into her gut when she wasn't careful and all she said was, "OW!"

It was a good thing she was treated on time before the injury got worse. But over all, why was she crying? He couldn't understand why.

"... Sonic Onii-san?"

 _Crap, she noticed me._

Should he run, or should he quickly escape? He didn't know and never knew how to deal with crying girls in his lifetime, yet he still decided to just walk over and sit beside her. After all, he should be grateful to her that she actually tolerated his short-temper whenever he couldn't get a skill right and kept on whining.

"So, why are you crying?"

 _Well, that came out awkwardly._

Sonatina wrapped her arms around her knees, her scarf covering the bottom half of her face, and was silent for a while. Then she replied, "I... I couldn't bring myself to do my job... I couldn't kill someone for real.."

Sonic frowned. So after all that training and seeing her power, she doesn't have the guts to really kill a human, after all? Was she serious?

"Are you such a scaredy cat? It's just a person, and you're an assassin, for god's sake," Sonic remarked haughtily and shook his head, "Just finish your job and it's all completed."

Her head snapped towards him, and Sonic saw an emotion that he had never seen in her eyes before.

Her eyes were flashing with fury.

"Oh, really?! Then how about you go to your village, grab a five-years-old child and kill him right now?!" Sonatina screamed at him in a shrilly voice.

It hit him. A child of aged five was the target of her assassination? He didn't mind killing off a whole group of people who were corrupted, but an innocent young child was another matter altogether.

"God damn it..." Sonic's attention reverted back to Sonatina, who was sniffling and wiping her tears with her scarf. "Does no one understand how I even feel, like, not at all...?"

"I... I'm sorry."

Sonatina shook her head. "It's okay, but now, Dr. Quattuor is probably furious that I didn't do the job at all... I can't go back."

He was curious. "Why not?"

"Don't you know what happens to an assassin who doesn't do his or her job properly?" Sonatina looked at Sonic, her tear-stained face seemingly calm. "They are tortured, beaten and then abandoned and left to die."

He could only stare at her, dumbfounded. No wonder she was crying. She was scared of going back, and was torn between escaping or facing punishment.

Because if the organisation managed to get their hands on her, she will face terrible consequences anyways.

"So what's your plan, Chibi? It's not like you can go back now, according to what you say."

Sonatina hugged her knees tighter, her head gripped in bony vise of knees. "... I don't know. I'm such a failure. I don't have a second blade for all types of circumstances in life, which makes me a failure of an assassin, doesn't it?"

Actually, both of them knew what they could do, but they didn't know how to convey it.

Sonic decided to speak up first. "How about... You stay over at my place for a while?"

Sonatina giggled, "Guess what? I was actually wanting to ask if I could if you didn't invite me."

Sonic chuckled along with her.

"Hey, Sonic Onii-san," Sonatina whispered as she turned to look at the lake, "Even though you find me annoying, you still tolerated me, and I'm really grateful for that. My family had already left me after a certain incident which caused their lives, and I would probably be abandoned again if you didn't decide to take me in. Thank you... for being such a great friend."

Sonic didn't know what that was, but something about what she said made him smile. Not the smile he has on when he's about to head for the kill, but a genuine, nice smile.

* * *

Deciding that he should have a break, the boy with the topknot switched on the television and plopped in front of it.

Just in case you're wondering, yes, the ninja village does run on electricity. Don't think that just because it's a town in the mountains mean that it's so isolated that no electricity goes there.

"Aaaaaand, Justice Man is here to save the day!" the character with the tacky suit and cape yelled before he beat up the villains on the TV programme.

"Oh my god..." Sonic groaned in frustration and flopped over the couch, face down. Was there nothing fun to watch on the television these days?!

"... Yo, you still alive?" Sonatina asked him, poking him while setting a bowl of udon on the coffee table. "Your mum made udon for you. Eat up."

Sonic deadpanned sarcastically, "I'M DEAD. I DIED OF BOREDOM. HOW CAN DEAD PEOPLE EAT."

Sonatina was confused till she saw what was on the television. "... Ah."

She sat down beside him and slurped up her udon just as Sonic sat up.

"So... I was wondering if you would like a superhero name."

"What? A superhero name? I'll like to keep my own name, thank you very much!" Sonic replied while putting a hand out to stop her from continuing.

Alas, it didn't work. "Hm... How about 'Speed o' Sound Sonic'?" Sonatina suggested as her eyes started to sparkle, her mind starting to work like a train on that would not stop as more ideas flowed into her head.

"What kind of a name is that?! It's like saying 'A Round Circle'!"

"Oh, and you can have purple as your main colour, since you have those purple streaks under your eyes! I happen to have a purple scarf that I usually wear, if you want!"

"ARE YOU EVEN LISTENING?!"

It was pretty hilarious how Sonatina was so serious about naming him like a superhero and Sonic was just screaming for her to stop.

"Come on, it sounds so cool! Unless you want me to make it into SOSS for short before turning it into 'Save Our Shitty Souls'."

"HEY! I'M NOT SHIT!"

"Well, you said it yourself."

"SCREW YOU!"

"Sorry, I don't wanna screw with you."

"... God damn it, Tina."

Sonatina turned to him with a look of surprise. "What did you just call me?"

"I called you Tina," Sonic replied, equally surprised, "Since Sonatina is a mouthful to say. You don't like it?"

"What do you mean by that? I love it!" Sonatina smiled brightly at him.

Sonic sighed in relief. "Well, that's great."

They were silently watching some random monster get smashed by the 'Justice Man' on screen when Sonatina suddenly asked,

"So... How about the name I gave you? Do you like it?"

"Does it look like I like it?"

"Aw."

* * *

"Tina? TINA?! Are you okay?!"

Sonatina awoke with a start to see Sonic sitting beside her, frowning in worry as he looked down at her. It was still dark outside, so why did he wake her up?

"Sonic Onii-san? What's wrong?" she asked him worriedly.

"I should be the one asking you that, Pipsqueak! Why were you sobbing in your sleep? And your sobs were getting harder and louder as time went by!" Sonic replied in a voice slightly higher-pitched and louder than usual. He was really agitated.

Sonatina lifted a hand to her face and realised that it was wet with tears. Some of her blue hair strands were stuck to her face and neck due to her sweating during her sleep.

"Oh..."

"Just what were you dreaming about? Did you dream about the organisation or something?"

"No..." Sonatina whispered softly, "I dreamt about them... My parents... My siblings... My family who died in that accident."

Sonic frowned. "I've always wanted to ask you this question, Tina. Just... what happened to you in the past?"

Sonatina sat up and leaned against her pillow, a serious look on her face. "Sonic Onii-san... Have you heard about the Sirens?"

He raised an eyebrow. "What do you mean? Who the heck are they?"

"... I should've known. The Sirens are always hidden from the sight of humans. No wonder nobody knows about us," Sonatina sighed before she looked back at Sonic with the same serious look. "Please! I need you to keep what I'm going to tell you after this a secret."

Sonic nodded, though feeling a little confused. "Okay?"

Sonatina took a deep breath and confessed, "I'm a Siren. I'm not a normal human being. In fact, I may even be considered as an 'Advanced Mysterious Being'."

"... Huh? What's that suppose to mean?"

Sonatina explained, "'Sirens' are a clan of what you guys call 'Mermaids' which can transform their tails into legs. We have blue hair with some variations and blue eyes, and we have blue fish tails, but we also tend to have another colour of fins. We are able to connect with the spiritual world, and most Sirens can sing well."

Sonic was confused, and found it all quite unbelievable. However, he still listened to what she had to say. "Spiritual world?"

Sonatina nodded. "We are able to use forms of energy for different uses, such as life energy and dark energy. The reason why I became a shadow after my bloodlust reaches a certain level is because of the emission of dark energy... But I guess you won't understand what I'm saying."

"Your ability has got to do with being a Siren? Then, what happened to your family?"

Surprisingly, Sonic was able to take the situation quite well.

Sonatina's expression faltered. "I... I was about three at that time... There was a huge thunderstorm and an earthquake... My family was caught in a tsunami, and the impact was so huge, it... It..."

She buried her head in her knees and sobbed, "It killed my whole family..."

Sonic didn't know what to say as she continued, "Why? Why am I the only one who survived? Why must I be the unlucky one who got taken by the organisation?! Why must I do something I hate?!"

 _So Sonatina actually didn't want to be an assassin? What was going on?_

"But if this is fate, then fine, whatever. It's not like I can change it anyway. I'll just go through this disgusting life till I die," Sonatina finished bitterly, her eyebrows scrunching up.

Sonic didn't know what to do, except to put an arm around her shoulders and reply, "It's going to be okay, we are all here for you. Please, don't just keep all of your feelings to yourself..."

There was a flash of lightning, a sudden clap of thunder, and Sonic could feel Sonatina jolt and quickly cover her ears, her eyes squeezed shut. Sonic frowned when he realised she was trembling and already starting to sweat. It wasn't that loud, so why did Sonatina had such a huge reaction to it? Then it hit him.

 _I'll be there for you. I promise._

Sonic put his free arm around Sonatina, enveloping her into a loose embrace. Sonatina just leaned into his chest, and wrapped her arms around his waist for support, sobbing quietly as he silently comforted her by awkwardly patting her back.

It was that night when a bond enveloped the both of them as they felt a closeness between them, stronger than ever before.

* * *

"Sonic Onii-san!"

Sonic turned to the blue-haired girl whose twin tails and scarf were fluttering behind her as she ran towards him. "What is it?"

Sonatina handed him a golden-coloured pendant which seemed to be a half of a whole pendant, and had the 'Yin' side of the 'Yin and Yang' symbol printed on it. The pendant dangled on a black string.

"Here! It's something I made!" Sonatina grinned as Sonic took it and gazed at it.

 _Wh... what the hell is this...?_

The pendant did look nice, and its handicraft was actually really good, but having a broken-into-half pendant made Sonic feel a little... disappointed for some reason.

"Uh, thanks," Sonic replied, but didn't hide the frown on his face.

"Don't look so disappointed! Look!" Sonatina smiled as she took out her pendant from under her shirt. It was the 'Yang' side of the pendant.

"If the two pendants connect, it'll form a full picture!" Sonatina added, "Isn't that awesome? It's a proof of friendship!"

Sonic stared at the pendant in wonder before he put it over his neck. Sonatina's smile grew even brighter, her two eyes of different colours shining with happiness.

A proof of friendship? That sounds so cliché, yet so innocently beautiful at the same time.

* * *

Sonic dashed through the forest, a panic-stricken look streaked on his face. His little ten-years-old friend had went into the forest, and didn't come back.

"Tina! Sonatina! Where the hell are you?!" Sonic shrieked in desperation.

There was no sign of her anywhere. Sonic was getting more and more terrified at the thought that something had happened to her.

"Get off me!"

Recognising the voice, Sonic immediately paused and turned to the source of the shout and the shuffling sound of scuffles and used his ninja skills to seemingly teleport there. The girl with sea blue twin tails was being harassed by a group of other people, along with a lady in a black coat who seemed to be the leader of the group.

Sonatina was trying but struggling to dodge the attacks by the other people, whom Sonic assumed to be the other trainee assassins from the syndicate that Sonatina came from. The lady pulled out an electric whip and quickly swung it, catching her leg and shocking her by spreading electricity throughout the whip. Sonic's fury rose when he heard Sonatina cry out a piercing shriek of pain and saw her tumble to the ground, unable to move.

"Stop hurting her!" he yelled angrily as he recklessly rushed towards the group and quickly knocked out the assassins trying to attack her. Sonic quickly stood in front of her in a defensive stance, trying to prevent anyone else from hurting her.

The lady who was watching the entire scene chuckled. "Oh my, a young boy trying to play hero by saving this young girl? So brave! I wonder how I should deal with you, seeing that you did knock out most of my more powerful trainee assassins..."

"Dr. Quattuor! Don't hurt him!" Sonatina screamed in fear, knowing what she would do to her friend. Her mismatched eyes screamed terror.

The lady, Dr. Quattuor, raised an eyebrow. "I see... So you're the one who took care of Sonatina when she left home? I ought to thank you. You've really raised her well. Her skills have improved drastically," she smirked.

Sonic's frown went deeper when he heard that. This wasn't going well...

"Therefore, allow me to let my little girl thank you..." she continued and walked towards Sonatina and forcefully pulled her up, causing her to let out a small groan in pain.

"Sonatina, I want you to thank this boy," she smiled brightly and placed a knife in Sonatina's hands. "Kill him and show him how powerful he has made you."

Sonic's and Sonatina's eyes widened in shock.

"What...?" Sonatina breathed out.

"Kill him, Sonatina. Kill him and I'll forgive you for not being able to do your job and abandoning the organisation," Dr. Quattuor repeated as her smile grew wider.

Sonatina's sweaty hands shakily gripped the knife as she stared at Sonic helplessly. "I... I..."

 _Is this how my life is going to end...?_

Flashes of his memories with Sonatina flooded into Sonic's mind. She was annoying, but kind and friendly. Why did something like this have to happen to such an innocent girl?

But she was like his little sister, one of the few brighter lightbulbs who managed to light up his life and fill him with a motivation to do something. If she died, will his life still stay the same as it always was? He could not bear to see her die just because she wouldn't kill him. He, on the other hand, didn't even have a reason for why he wanted to become the strongest ninja in the world.

 _Why should I continue to live if I have to question even my own beliefs in life?_

Smiling weakly, Sonic sighed and told the girl, "Tina, you still have a future ahead of you. I want you to survive... and just kill me."

"What?" Sonatina's fearful expression faltered into confusion before it turned into fear again. "I can't do that! You're my first and only friend! How am I suppose to kill you?!"

"Listen, I won't blame you if you drive that knife into me. I'm even questioning my own beliefs in life. Do you think someone like me has the will to live?"

However, as much as he tried, Sonatina shook her head stubbornly and threw the knife onto the ground. "NO! I won't do that! I won't allow it! Even if you don't have a will, think about your mom! Will she be happy that her son sacrificed himself just for this one stupid kid?!"

Suddenly, clapping echoed throughout the area. The leader of the organisation laughed maniacally as she remarked, "Oh, how touching! But no matter what, you're still going to die anyways."

That was when more assassins came out of the clearing and circled around the fifteen-years-old ninja, who glared at them with his grey eyes.

"Sonic Onii-san! Run! Those aren't amateur assassins! They're the professional ones in the organisation! You may be strong, but you can't beat them!" Sonatina screamed in terror as she watched the horrifying scene through her mismatched eyes.

It was too late. One of them had already teleported over and slashed Sonic's chest on the left deeply, causing blood to gush out and Sonic to crash to the ground due to the sudden force. A gasp in Sonic's throat hitched as his eyes widened, unable to believe that the pain was even worse than he had expected.

Dr. Quattuor's red eyes turned into that of a goat's as she grinned darkly and sadistically, and ordered with a smirk, "Kill him."

Sonic was fighting a losing battle. The assassins were a lot more stronger and professional than he was, and he was already badly wounded, with deep cuts everywhere on his body.

Staggering to his feet, Sonic growled as blood ran down his face, about to go berserk. "Quattuor... I won't let you hurt my closest friend!"

"Closest friend? Really?" Dr. Quattuor let out a haughty laugh before her facial expression turned cold. "Kill this brat immediately."

"STOP IT!" Sonatina screamed as Dr. Quattuor pulled her scarf back, threatening to strangle her to refrain her from helping the ninja out.

The leader of the syndicate raised a hand and the assassins stopped attacking Sonic. Sonic tumbled to the ground, exhausted and bleeding badly as he panted, his lungs aching for air and his throat parched. He could feel his energy and consciousness slowly fading away from him.

"Didn't you guys listen to little Sonatina here? Stop attacking her friend," she commanded before an evil glint flashed in her eyes as she continued, "Throw him into the lake."

Before Sonic or Sonatina could react, in one swift motion, Sonic's body hit the water of the lake, dying the water a blood red colour. Pain surged through his body as the water stung his wounds, causing unconsciousness to flood his mind faster.

Sonic tried to scream and thrash about as fear surged into his heart; he didn't have the ability to swim, which meant that he would definitely die at this rate.

As he caught sight of a sudden flash of blue and yellow tail swooping past him, all Sonic could do was to close his eyes and black out as he thought,

"I couldn't protect my only friend..."

* * *

His eyes flew open. Sonic shot up and looked around. How the heck was he suddenly back in his room? Was he dead?

He checked his body. There were a lot of scars, alright... But there was no bleeding wound.

 _How did that happen? Was everything a dream, all along?_

Sonic suddenly heard footsteps, and his mother stepped into the room. "How are you feeling now, Sonic?" she asked in a kind but worried tone as she sat beside him on his bed.

"Tina... Where is she? What happened to her?!" Sonic asked his mother anxiously as he grabbed onto her hand.

"She... left a letter for you," was all she could reply before she set the paper on his end table before she walked out, continuing, "You may want to read the letter before you do anything rash, Sonic. I'll go and get a bowl of soup for you."

As his mother closed the door, Sonic snatched up the letter and read it.

 _Sonic Onii-san,_

 _Somehow, I managed to save you from drowning and use my life energy to heal most of your wounds. I'm sorry that I couldn't heal your scars. My powers as a Siren aren't that strong yet. Hopefully, your scars will fade on their own?_

 _Regardless, if I'm gone, please don't try to find me, because you'll only be facing more danger. I'm really sorry for pulling you into this bunch of mess. I know this sounds cliché, but you're the best friend and Onii-san that I would ever have in my life. Thank you for tolerating my annoying self and comforting me when I needed it. I know this is not the time to ask this, but I wonder whether you still hate the superhero name that I gave you that day?_

 _With love,_

 _Sonatina_

Realising what Sonatina had meant, Sonic quickly changed into his clothes, redid his topknot, grabbed his weapons and quickly ran out of his house, ignoring his mother's shouts after him and dashing through the forest.

Panting, he came to a stop in front of an abandoned dojo. Sonatina had told him before that the abandoned dojo was their base in the forest. Sonic slammed the door open and rushed in, only to be greeted by an empty room with some papers strewn here and there.

He was too late.

With a shaky step, Sonic stepped into the room and looked around with widened grey eyes of disbelief, trying to catch sight of a blue head. However, it had all been in vain.

Just as he was about to give up, he saw a flash of purple at the corner of his eye and quickly grabbed it.

It was the purple scarf that Sonatina always had with her.

Come to think of it, purple didn't suit her at all, especially with that blue and white hair and mismatched blue and yellow eyes. Why the heck was she wearing purple in the first place? But... It was these kinds of strange things about people that made their loved ones think about them... and miss them.

Sonic never cried in his entire life except when he was a little baby who didn't know the way of life yet, but the loss of his friend made him drop onto his knees and break down, clutching onto the scarf as he cried for the first time in years.

 _"Why are you so bent on becoming the strongest?"_

But it was also at that point when he realised that he now had a reason to the question Sonatina had asked two years ago.

Wiping his tears, Sonic slowly stood up and his eyes flashed with determination. As he wounded the purple scarf around his neck and stepped out of the dojo, he muttered,

"To be able to protect you once I manage to find you."

 _A few years later..._

"C'mon, Dante! You can't be serious about that!" a short man with short green hair guffawed when he heard about his friend's achievement as they walked down an alleyway.

"Oh, but I did finish the task that Dr. Quattuor gave me and killed off that stupid Crimson Rose guy, Marvin," the other bulkier male with his orange hair tied into a small ponytail laughed.

"And he was supposed to be one of the world's top ten strongest assassin? You've got to be kidding me," Marvin snickered and shook his head.

Suddenly, someone dropped down in front of them and asked, "So I heard you were under someone called Dr. Quattuor?"

The two men eyed the guy who appeared in front of them. He had a topknot, grey eyes, purple streaks under his eyes and a purple scarf which looked strikingly familiar wounded around half of his face and his neck, thus concealing his identity. There was a sword on his back, and he was holding something with a string attached to it.

"What do you want, Sir?" Marvin asked in an innocent tone.

"I want to ask you a few questions. Is that blue-haired female assassin with mismatched eyes still with you?" the strange male asked.

Dante replied. "You mean, that girl named Sonatina? She had already left a few years ago. How stupid of her, though. That incident had caused our organisation some problems, and we're now searching for her."

"... And what exactly will you be doing?" he asked again.

"Why, of course it's to get rid of her! And after that-"

At that moment, his head flew off. Dante's head rolled across the floor like a bowling ball. Blood spilled everywhere and splattered onto his partner.

"Wh... What the hell are you doing?!" Marvin shrieked as he grabbed his pistols and tried to shoot the ninja, who was holding his sword. However, the ninja proved to be too fast for him.

"I recognise you... You were one of the assassins who tried to kill Tina and me a few years ago, weren't you? Well, allow me to return you the favour."

Marvin felt a dart ram though his head and into his skull, damaging his brain. He fell to the ground.

"Man, I thought you guys were professional assassins. I didn't expect myself to beat you two so easily," the ninja chuckled.

"Just... Who the hell are you..?" Marvin asked as he breathed his last.

As the ninja walked away, he kept the golden pendant with the 'Yin' half of a 'Yin and Yang' symbol printed on it into his pocket, pulled down his scarf to reveal his creepy grin, and said,

"I'm Speed o' Sound Sonic. Nice to kill you."

-End-


End file.
